The present invention relates to plate heat exchangers generally, and, particularly, to the manufacture thereof.
Plate heat exchangers are well known in the art. One example of these is U.S. Pat. No. 5,069,276, to the present inventor, which discloses a plate heat exchanger having a plurality of stacked, substantially flat panels defining between them, in the stacked state, spaces which are formed so as to permit therethrough a flow of a heat exchanging medium. Such stacks may have upturned edges, so as to have a shallow trough-like configuration when viewed in cross-section. It is well known to connect the upturned edges of these plates together by various welding techniques, including brazing.
It will be appreciated, however, that welding together of a stack of heat exchanging plates is very time intensive and, due to the thinness of the plates, can weaken the plates and, in general, cause results which vary in quality. Furthermore, while, the edges of adjacent plates may be connected in this manner, it is not possible to connect mid-portions thereof, thereby requiring provision of external mechanical means, such as support rods which extend laterally through the plates and lengthwise through a stack.
The present invention seeks to provide an improved method of forming a heat exchanger stack, overcoming disadvantages of known art.
There is thus provided, in accordance with a preferred embodiment of the invention, a method of forming a heat exchanger stack from a plurality of plates, wherein the plurality of plates includes at least first and second nestable plates formed of an electrically conductive material, each having a generally flat central portion and at least a pair of edge portions generally non-coplanar relative to the respective central portions of the plates, wherein each plate has a plurality of protrusions which is formed so that, when the plates are in a stacked, nested position, the respective pluralities of protrusions of the first and second plates engage each other, such that the respective central portions of the plates are spaced apart, thereby to define therebetween a space through which a heat exchanging medium may be passed, wherein the method includes:
placing the first heat exchanging plate on a support;
placing the second heat exchanging plate in nesting arrangement with the first heat exchanging plate such that the central portions and the edge portions of the two plates are spaced apart; and
exposing at least the edge portions of the second heat exchanging plate to pulsed electromagnetic energy, so as to apply thereto a kinetic force causing the edge portions to bend away from the pulsed electromagnetic energy source, such that they impinge on the respective edge portions of the first plate, so as to become joined thereto.
In a further embodiment, the first heat exchanging plate is placed on a surface of a shaped cavity within the support.
In accordance with an alternative embodiment of the present invention, there is provided a method of forming a heat exchanger stack from a plurality of plates, wherein the plurality of plates includes at least first and second plates formed of an electrically conductive material, each having at least a generally flat central portion and a pair of edge portions, wherein each plate has a plurality of protrusions which is formed so that, when the plates are in a stacked position, the respective pluralities of protrusions of the first and second plates engage each other, such that the respective central portions of the plates are spaced apart, thereby to define therebetween a space through which a heat exchanging medium may be passed, wherein the method includes:
placing the first heat exchanging plate on a support;
placing the second heat exchanging plate in nesting arrangement with the first heat exchanging plate such that the central portions and the edges of the two plates are spaced apart; and
exposing at least the central portion of the second heat exchanging plate to pulsed electromagnetic energy, so as to apply thereto a kinetic force causing the protrusions of the second heat exchanging plate to become joined to the protrusions of the first heat exchanging plate.
In a further embodiment, the first heat exchanging plate is placed on a surface of a shaped cavity within the support.
Preferably, the edge portions of the plates are generally non-coplanar relative to the respective central portions of the plates, so as to be nestable,
and wherein the method also includes the step of exposing the edge portions of the second heat exchanging plate to pulsed electromagnetic energy, so as to apply thereto a kinetic force causing the edge portions to bend away from the pulsed electromagnetic energy source, such that they impinge on the respective edge portions of the first plate, so as to become joined thereto.
The present invention also provides a heat exchanger stack formed in accordance with the method of the invention.